Diagnostic accuracy of four handheld dynamometer tests for identifying individuals with hamstring interlimb strength asymmetry

Abstract

Introduction: Handheld dynamometer (HHD) strength tests are widely used in clinical settings. The limb symmetry index (LSI) is a key parameter for guiding rehabilitation progression and return-to-sport decisions following hamstring muscle injuries. However, it remains unclear whether HHD-derived results can accurately identify individuals with interlimb strength asymmetry. Objective: To evaluate the diagnostic accuracy of four HHD tests for identifying individuals with hamstring interlimb strength asymmetry, using isokinetic dynamometry as the reference standard. Methods: Thirty physically active young men underwent concentric and eccentric isokinetic tests at 60°/
seconds and four isometric HHD tests (test A: prone, knee at 90°; test B: prone, knee at 30°; test C: supine, knee at 90°; test D: seated, knee at 90°) in random order on two separate days. LSI values derived from isokinetic dynamometry were used as the reference standard. Interlimb strength asymmetry was defined as LSI < 90% or > 110%. Sensitivity, specificity, predictive values, overall accuracy, and area under the receiver operating characteristic (ROC) curve were calculated. Results: LSI values obtained from HHD tests showed no significant or only weak correlations with isokinetic measures. Diagnostic accuracy ranged from 46.7 to 60% for identifying concentric asymmetry and from 46.7 to 63.3% for eccentric asymmetry. The area under the ROC curve values ranged from 0.418 to 0.696, indicating limited discriminatory ability. Conclusion: None of the four hamstring HHD tests demonstrated sufficient accuracy to identify individuals with interlimb strength asymmetry when compared with concentric or eccentric assessments performed on an isokinetic dynamometer.